MRSA 'spread by patient transfers'

10:45Tuesday 15 May 2012

New research has mapped the way that MRSA “superbug” bacteria spread, BBC News has reported. The results suggest that antibiotic-resistant bacteria may often spread from large, inner-city hospitals to smaller regional ones when patients are transferred.

The way that superbugs spread has been researched as part of an intricate study conducted by Scottish researchers, who looked at samples taken across the UK over 53 years. The researchers used genetic techniques to scan patterns and mutations within the various samples and to build up a “family tree” showing how a particular strain (called EMRSA-16) has spread between different hospitals across the country. They found that EMRSA-16 has generally spread by transmission from hospitals in large population centres in London and Glasgow to regional healthcare settings. The researchers suggested that patients’ referrals are an important cause of the spread of this bug across the country.

This type of study can provide useful estimates of transmission routes of MRSA, although there is still a need for further research incorporating a larger number of sampled hospitals to determine the wider UK pattern.

MRSA can be prevented through effective hand washing and screening before hospital admission. Find out more about preventing MRSA.

The study was carried out by researchers from the University of Edinburgh and was funded by various research grants, as well as US governmental organisations including the National Institute of Allergy and Infectious Diseases, the National Institutes of Health and the Department of Health and Human Services. The study was published in the peer-reviewed journal Proceedings of the National Academy of Sciences USA (PNAS).

The story was covered accurately by BBC News.

This study used genetic analysis of bacteria samples to map the way a particular form of MRSA spread between patients and hospitals across the UK. It collected information from infected patients in the UK over 53 years and looked at the emergence and transmission of EMRSA-16, a major clone (type) of MRSA. The study identified genetic elements and mutations of EMRSA-16 that allowed it to spread between patients and hospitals across the county.

MRSA (meticillin-resistant staphylococcus aureus) is a type of bacterial infection that is resistant to a number of widely used antibiotics. It is often referred to as a “superbug”. MRSA infections are more common in hospitals because patients often have an entry point, such as a surgical site, which allows the bacteria to enter the body. Also, bacteria can easily spread through direct contact with other patients and staff or contaminated surfaces.

Proper hand washing and screening are effective methods used to prevent MRSA infections from occurring. Rates of MRSA have fallen in recent years because of increased awareness of infection by both medical staff and the general public. However, it still places a considerable strain on the health system as it is more difficult to treat than other types of bacterial infection. Currently, all patients who go to hospital for a planned procedure are offered a swab test to see whether they are carrying MRSA bacteria.

Researchers looked at the genetic make-up of more than 80 variations of a major clone of MRSA called EMRSA-16 found in hospitals. Samples were collected from infected patients during a 53-year period. The EMRSA-16 clone of MRSA predominantly occurs in hospitals, and the researchers estimated that it has been present in UK hospitals for about 35 years. Researchers then identified genetic elements and mutations in the bug and tracked how these spread between patients and hospitals across the country.

Researchers used a specialist approach to map part of the genetic make-up of each sample, looking for changes and patterns in its genetics. In effect, this allowed them to build up a “family tree” showing how different strains had developed.

The key finding of this study was that EMRSA-16 has spread within the UK by transmission from central hospitals serving large populations to smaller, regional healthcare settings. It found that Glasgow in west Scotland was a hub for transmission to 16 surrounding regions in the north and east of Scotland. Similarly, in London EMRSA-16 spread from large city hospitals to smaller surrounding hospitals in south and southeast England.

Study lead Dr Ross Fitzgerald reported that “our findings suggest the referral of patients to different hospitals is a major cause of MRSA transmission around the country.” He also said that “variants of MRSA circulating in regional hospitals probably originated in large city hospitals.”

The researchers concluded that these findings could help prevent the spread of drug-resistant infections such as MRSA.

This study estimates how a strain of MRSA (EMRSA-16) may spread from hospitals in major UK cities to smaller regional healthcare settings. Findings from this study are supported by findings of a recent US study, which estimated high transmission routes from large hospitals to long-term care facilities.

The researchers note that the dataset used is limited by the relatively small number of hospitals sampled. Despite its interesting findings, further research is required that incorporates a larger number of sampled hospitals to determine the pattern of spread elsewhere in the UK.

Collecting data on the prevalence and spread of superbugs such as MRSA (medically known as surveillance) plays an important role in containing and eradicating potentially harmful bacteria in medical settings, and ultimately reducing the number and severity of hospital-acquired infections. When used strategically, data of this type, along with simple but effective measures such as thorough hand washing, can make a difference to the spread of infections, as illustrated by the recent fall in MRSA in NHS hospitals.